This is a no-op refactoring for test.
Currently, shouldTestThisNetworkType method check test
preconditions and generating network traffic for testing.
Decouple these two functionalities to allow follow-up
changes to capture data usage baseline prior to
generating network traffic.
Test: atest CtsNetTestCases:android.net.cts.NetworkStatsManagerTest \
--rerun-until-failure 30
Bug: 368624224
Change-Id: I5510184ec0cf8afa05b46f78ebaf80e500abaeeb
359d23059c